The study will evaluate the effectiveness of Botulinum Toxin (BTX) in reducing spasticity and improving function and mobility in children with spastic diplegia, a common form of Cerebral Palsy (CP). We will measure the effects of the intervention across the five domains of science related to disability: pathophysiology, impairment, functional limitation, disability and societal limitation. The design is a prospective, randomized, double-masked clinical trial with a six-month evaluation period. Forty (40) children ages 4-12 years will be recruited and randomized into two groups. Group A will receive BTX. Group B will receive a placebo. Outcomes will be assessed in a masked evaluation at baseline, 3 weeks, 8 weeks, 12 weeks, and 24 weeks. Group B subjects will have the opportunity to receive BTX treatment after 24 weeks.